Method in the Preparation of Samples for Microscopic Examination, and Apparatus for Checking the Coverslipping Quality of Samples

ABSTRACT

The invention relates to a method in the preparation of samples for microscopic examination onto which a coverslip is applied. The method is notable for the fact that the coverslipping quality is checked automatically and at least partly optically. The invention further relates to an apparatus for carrying out the method, and to an apparatus for checking the coverslipping quality of samples onto which a coverslip is applied.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/769,859 filed Feb. 19, 2013, which claims priority of German patentapplication number 10 2012 101 377.2 filed Feb. 21, 2012, the entiredisclosures of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a method in the preparation of samples formicroscopic examination onto which a coverslip is applied. The inventionfurther relates to an apparatus for checking the coverslipping qualityof samples onto which a coverslip is applied.

BACKGROUND OF THE INVENTION

In preparation for microscopic investigations, the samples to beinvestigated, which can e.g. involve a histological section, are usuallyplaced onto a specimen slide and treated with a coverslipping medium,which preferably has a refractive index adapted to the refractive indexof the coverslip or of the specimen slide and functions as an adhesive,before a coverslip is then applied. Because coverslipping of the sampleis usually a very time-consuming procedure, coverslipping machines areoften used for this.

An apparatus for handling specimen slides and coverslips is known, forexample, from DE 101 44 048 A1. With this apparatus, a coverslip isrespectively received with the aid of a receiving unit guided via anactuation arm, and set onto a desired position on the specimen slide.

A variety of defects can occur in the process of coverslipping. Forexample, it may happen that the coverslip completely or partlyfractures, which can result in the emergence of coverslipping medium asa further defect. As a further defect, air inclusions beneath thecoverslip can occur; these can have a disadvantageous influence on alater microscopic investigation, or make it in fact impossible.

When defects occur in the coverslipping process, they are often noticedonly upon microscopic examination. This leads to a number of seriousproblems for routine laboratory operation, since at this point it timeit is often not possible to re-coverslip the sample. Especially when aplurality of samples are to be investigated, for example in a continuousthroughput, such defects result in a considerable diminution in theoverall investigation efficiency of the laboratory, since the entireprocess sequence, and not just the coverslipping process, becomesdisrupted.

U.S. Pat. No. 5,566,249 discloses an apparatus for detecting air bubblesin the coverslipping medium. The apparatus comprises image-generatingmeans with which an image of the coverslip can be generated, and whichcan be embodied as an automated scanning microscope. Means forrecognizing bubble edges, and for further image processing, are alsoprovided.

SUMMARY OF THE INVENTION

The object of the present invention is to describe method which makes itpossible to avoid or at least mitigate the problems recited above.

The object is achieved by a method which is characterized in thatcoverslipping quality is checked automatically and optically at leastpartly with dark field illumination.

The further object of the present invention is to describe an apparatusthat enables rapid and reliable checking of coverslipping quality insamples onto which a coverslip is applied.

The further object is achieved by an apparatus that is characterized byan optical imaging apparatus operating automatically and at least partlywith dark field illumination.

It has been recognized in accordance with the present invention that aplurality of problems that can occur during routine laboratory operationas a result of defectively coverslipped samples can be at leastmitigated by early and reliable checking of coverslipping quality. Anearly check as to whether a sample is defectively coverslipped, andpreferably an identification as to the nature of an identified defect,make it possible to keep the subsequent laboratory processes, inparticular microscopic examination, largely free of defectivelycoverslipped samples. The possibility is also created ofcontemporaneously eliminating coverslipping defects that are identified,for example by re-coverslipping.

In a particular embodiment of the invention, a check is made as towhether the coverslip is damaged after a coverslipping operation, inparticular as to whether the coverslip exhibits a fracture after acoverslipping operation. Alternatively or additionally, provision can bemade that a check is made as to whether air inclusions are present in acoverslipping medium and/or as to whether air inclusions are presentbetween the coverslip and the sample. Provision can furthermore be made,alternatively or additionally, that a check is made as to whethersurface irregularities of the coverslip are present.

In order to carry out the checks recited above, advantageously at leastone, preferably microscopic, image of the coverslip and/or of thecoverslipping medium can be generated. Provision can be made inparticular that a grayscale image is generated as an image. Thegeneration of an image of the coverslip and/or of the embedding mediummakes possible, especially if digital image data are generated, anautomatic, for example computer-controlled evaluation with regard to thepresence and/or nature of coverslipping defects. Provision can inparticular be made here that the image patterns of known coverslippingdefects and/or of particularly frequently occurring coverslippingdefects are stored in a memory, and are compared with image details ofthe generated image.

The coverslip and/or the embedding medium is suitably illuminated inorder to generate the image, in which context provision can be made inparticular that the image is generated with bright field illumination.It has been found that it is particularly advantageous firstly togenerate a first image under bright field illumination in order toclassify the imaged objects and optionally compare them with referencepatterns.

Acquisition of an image occurs preferably in the context of an axiallysymmetrical arrangement of the (incident) bright field illuminationsystem and camera with respect to the specimen slide, the result beingthat a largely parallel wavefront strikes the entire surface of thecoverslip, and reflects well and is therefore also easily detectable.The object located beneath the coverslip remits the light, and a portionof that light also travels to the detector.

Coverslipping defects, such as air inclusions, surface irregularities,or glass fracture, result in reflections of the illumination light thatsubstantially differ from the reflections that occur in the context of asample coverslipped without defects. This becomes particularly clearlyapparent in a grayscale image. In this, air inclusions result inincreased reflection and appear in the image as bright regions. Surfaceirregularities and fractures in the coverslip deflect the light andappear in the image as particularly dark regions, since less lighttravels from these regions to the detector.

A determination is preferably made, by calibration, of the optimumexposure time allowing the background to be imaged in the neutral-grayregion, so that particularly bright and/or particularly dark regionsstand out particularly well from the background.

When the sample is illuminated with a directional illumination, inaddition to reflection of the illumination light at the air-glassinterfacial layer a reflection also occurs at the interface between anenclosed air bubble and the coverslipping medium (adhesive) surroundingit. A double reflection therefore occurs in the case of an air bubble,so that air bubbles appear in the image as very particularly brightregions. It is preferred to use those materials and angles of incidencewhich ensure that the reflectance of the background exceeds a specificvalue, so that the reflection of the air inclusions is always greaterthan the reflections at other components, for example at interfaces ofthe specimen slide or of the coverslip. To ensure this, for example,specimen slides or coverslips having particular optical coatings can beused.

By preference, all the parameters are selected so that the backgroundappears with a grayscale value of 100, while air inclusions exhibit inthe image a grayscale value of approximately 200. It has been found thatthe detection of air inclusions functions reliably if they exhibit acontrast of at least 20% with the background.

A deviation of the surface geometry of the coverslip from an idealplanar surface causes incident light to be reflected with a doubleangular error. In addition, the light reflected from the coverslip nolonger exhibits a completely flat wavefront. The detection geometry ispreferably selected in such a way that the light reflected from thefault does not travel to the detector. The image of the fault thusappears darker than the background. The detection distance, the size ofan entrance opening of the detector, and the aperture of the detector(for example, camera) are, in particular, to be selected accordingly.

In a particularly advantageous embodiment, contours of the regions thatexhibit a contrast of more than 20% with the background are calculated,for example by an evaluation apparatus. The regions identified can thenbe filtered in terms of grayscale values, and associated withcoverslipping defects.

Alternatively or in addition to the generation of an image with brightfield illumination, provision can also be made that an image with darkfield illumination is generated. A very particularly precise andreliable embodiment is one in which firstly a first image is generatedin bright-field in order to classify the imaged objects, and then asecond image is generated with a dark field illumination in order toachieve a more precise classification of the objects found in thecontext of bright field illumination.

A dark field illumination is notable in particular for the fact that theillumination light is incident onto the object with sufficient obliquitythat the reflected illumination rays are not incident into the objectiveand thus do not contribute to image creation. The result achievedthereby is, in particular, that exclusively refracted or scattered lightcontributes to image creation. Advantageously, the object structuresthen usually appear as bright on a dark background.

Dark field illumination is achievable, for example, by illuminating at aflat angle (large angle of incidence of the illumination light relativeto the surface normal of the coverslip). Bright, sharply delimitedobjects then appear in the image, with high contrast with respect to thebackground. Provision can be made in this context that the illuminationexhibits a semicircular pattern, so that the detected object contoursare thus not complete and continuous.

For accurate classification of the half-discovered image objects, anadditional check can be made in the image generated with dark fieldillumination as to whether artifacts (e.g. particular reflections) occurat the same location in the image. It is thereby possible to distinguishparticularly reliably whether artifacts detectable in one of the imagesare to associated with a coverslipping defect or are, for example,caused by the specimen itself.

As already mentioned, provision can advantageously be made that theimage or images is or are automatically evaluated by an evaluationapparatus, and/or that the image or images is or are automaticallyevaluated by an evaluation apparatus comprising a data processingdevice, in particular a PC. An embodiment of this kind is not onlyparticularly fast, but moreover also particularly reliable and precise.

As already explained, an embodiment in which both an image with brightfield illumination and an image with dark field illumination aregenerated, and in which the images are then compared with one another(for example by an evaluation apparatus), gives information inparticularly reliable fashion as to whether a coverslipping defect ispresent, and which coverslipping defect is involved. This isparticularly reliable when a check is made (for example, by anevaluation apparatus) as to whether, for a detected detail of the oneimage, a correspondence is present in the other image.

In a particular embodiment, provision is made that the image acquisitionangle and/or the illumination angle is individually adjusted in a manneradapted to the nature and size of the sample to be investigated. It canbe advantageous in this context to use an apparatus which allows theimage acquisition angle and/or the illumination angle to be (preferablysteplessly) adjusted.

An apparatus of this kind furthermore has the advantage that it can beused both to generate an image with bright field illumination (forexample with a 0° angle of incidence of the illumination light) and togenerate an image with dark field illumination (for example with anangle of incidence for the illumination light in the range from 50 to80°. In particular, with an apparatus of this kind the sample can remainon the sample stage and/or in a sample mount after a bright field imageis generated, and dark field illumination can be generated immediatelyafter modifying the image acquisition angle and/or the illuminationangle. Provision can be made in particular that the illumination lightsource and/or the detector (for example, camera) are each mounted onpivotable stand arms. Alternatively or additionally, it is also possibleto pivot the respective beam paths, for example with the aid ofrotatable mirrors.

Particularly reliable results are achieved if the average brightnessand/or the brightness distribution of a reference image, in particularof a coverslipped specimen slide without a sample, is measured—manuallyor automatically—before the coverslipping quality is checked. Thegrayscale value distribution of the reference measurement is preferablystored so that it can be compared with the grayscale value distributionof subsequent images in the context of the investigation of coverslippedsamples. In particular, a shading correction can be carried out (forexample, by an evaluation apparatus) for each image with the aid of thereference measurement, in particular on the basis of the measuredbrightness and/or brightness distribution. Because ambient conditionscan change over time, provision can advantageously be made that thecalibration operation is repeated at predefined or acceptable timeintervals. Relevant changes in ambient conditions can be, for example,the ambient temperature or the modified radiating behavior of an agingillumination light source.

In particular, provision can advantageously be made that from themeasured average brightness and/or brightness distribution, an exposuretime for generating an image is calculated, and/or that from themeasured average brightness and/or brightness distribution, an exposuretime for generating an image is calculated in such a way that apredetermined or predeterminable brightness for the background isachieved.

In a particular embodiment, provision is made that firstly an overviewimage is generated and/or that a sample-specific code, in particular abarcode attached to a specimen slide or to a coverslip, is read out.Provision can be made in particular that the overview image is generatedwith an imaging apparatus for checking coverslipping quality, and/orthat a sample-specific code, in particular a barcode attached to aspecimen slide or to a coverslip, is read out with an imaging apparatusfor checking coverslipping quality.

An embodiment of this kind has the advantage that the sample to beinvestigated can be identified and, for example, associated with apatient, on the basis of features that have nothing to do with thedetection of coverslipping defects. Provision can moreover be made thatin addition to a check for coverslipping defects, the staining quality,in particular the staining quality of a hematoxylin-eosin stain, and/ora color intensity, can be checked. The same apparatus that is also usedto check coverslipping quality can be used in this context. This has theparticular advantage that an additional apparatus is unnecessary, andthat the sample does not need to be transferred into a furtherapparatus; the ultimate result is that time can be saved.

As already explained with reference to examples, provision can be madethat the same coverslipping result is checked in chronologicallysequential fashion under different conditions, and/or that the samecoverslipping result is checked in chronologically sequential fashionunder different conditions at different testing stations.

As already mentioned, an imaging apparatus, in particular an imagingapparatus having dark field illumination, can be used particularlyadvantageously to check the coverslipping quality of samples onto whicha coverslip is applied.

In a particular embodiment of an apparatus according to the presentinvention for checking the coverslipping quality of samples, whichcomprises an automatically operating optical imaging apparatus, aevaluation apparatus, preferably operating automatically, thatinvestigates at least one image generated by the imaging apparatus isadditionally provided. Provision can be made in particular that anevaluation apparatus of this kind investigates an image generated by theimaging apparatus as to whether the coverslip is damaged after acoverslipping operation and/or whether the coverslip exhibits a fractureafter a coverslipping operation and/or whether air inclusions arepresent in a coverslipping medium and/or whether air inclusions arepresent between the coverslip and the sample and/or whether surfaceirregularities of the coverslip are present.

For this purpose in particular, provision can be made that the imagingapparatus generates at least one image of the coverslip and/or of thecoverslipping medium, and/or that the imaging apparatus generates atleast one microscopic image of the coverslip and/or of the coverslippingmedium, and/or that the imaging apparatus generates a grayscale image.

An advantageous embodiment of an apparatus according to the presentinvention contains an illumination apparatus for illuminating thecoverslip and/or the embedding medium upon generation of an image, inwhich context the illumination apparatus can be designed to generate abright field illumination and/or a dark field illumination. As alreadymentioned, provision can advantageously be made here that both a brightfield illumination and a dark field illumination is generated with oneand the same illumination apparatus.

Provision can be made in particular that the evaluation apparatuscalculates, from a measured average brightness and/or brightnessdistribution of a reference image, in particular of a coverslippedspecimen slide without a sample, an exposure time for generating animage, and/or that the evaluation apparatus calculates, from a measuredaverage brightness and/or brightness distribution of a reference image,in particular of a coverslipped specimen slide without a sample, anexposure time for generating an image in such a way that a predeterminedor predeterminable brightness for the background is achieved upongeneration of the image.

As already mentioned, provision can advantageously be made that theapparatus is embodied to generate an overview image and/or to read out asample-specific code, in particular a barcode attached to a specimenslide or to a coverslip. In particular, the apparatus can advantageouslybe embodied to check the same coverslipping result in chronologicallysuccessive fashion under different conditions and/or at the differenttesting stations.

In a particular embodiment of the apparatus according to the presentinvention that exhibits a particularly high level of automation, ahandling apparatus that conveys a coverslipped sample to be investigatedinto a scanning region of the imaging apparatus is provided. Provisioncan be made here in particular that the handling apparatus operatesautomatically.

A handling apparatus of this kind can, for example, sequentially removecoverslipped samples to be investigated from a receiving apparatus, inparticular from a stacking shelf, and transfer them into a scanningregion of the imaging apparatus. Provision can furthermore be made thatthe handling apparatus deposits each sample back into the receivingapparatus after it has been checked.

An apparatus for checking coverslipping quality can be part of acoverslipping machine and/or can be integrated into a coverslippingmachine. Both coverslipping and checking of coverslipping quality canthus occur in a single arrangement. Provision can furthermore be madethat the coverslipping operation is repeated, in particularautomatically, if a coverslipping defect has been identified.

Alternatively to integration of the apparatus for checking coverslippingquality into a coverslipping machine, provision can also be made thatthe apparatus for checking coverslipping quality is embodied to, inparticular automatically, receive at least one sample equipped with acoverslip from a coverslipping machine, or to remove it from acoverslipping machine.

To allow even a larger number of samples to be reliably analyzed andprocessed in a short time, provision can advantageously be made thatdata regarding coverslipping quality, and/or a sample-specific code, inparticular a barcode attached to a specimen slide or to a coverslip, aretransferred to a higher-level data processing system. Alternatively oradditionally, provision can be made that data, for example dataregarding coverslipping quality, and/or a sample-specific code, inparticular a barcode attached to a specimen slide or to a coverslip,and/or data regarding patient data to be associated with the sampleand/or regarding the current whereabouts of the sample, are exchangedwith a higher-level data processing system.

According to a particular inventive concept, particularly reliableprocessing and investigation, in particular even of larger quantities ofsamples, is possible with a sample processing system that is equippedwith an apparatus according to the present invention. This can comprise,in particular, a higher-level data processing system that receives dataregarding coverslipping quality, and/or a sample-specific code, inparticular a barcode attached to a specimen slide or to a coverslip,and/or data regarding patient data to be associated with the sampleand/or regarding the current whereabouts of the sample, from theapparatus for checking coverslipping quality. The higher-level dataprocessing system can comprise, in particular, a memory for storingthese data. Provision can also be made that the received data arecompared with previously stored data, for example in order to controlfurther processing of the sample. Provision can also be made that thesample processing system comprises a higher-level data processing systemwith which the apparatus for checking coverslipping quality exchangesdata, for example data regarding coverslipping quality or thewhereabouts of the sample, or regarding patient data to be associatedwith the sample.

Further objectives, advantages, features, and utilization capabilitiesof the present invention are evident from the description below of anexemplifying embodiment with reference to the drawings. All featuresdescribed and/or illustratively depicted, of themselves or in any usefulcombination, constitute the subject matter of the present invention,independently of their grouping in the claims or their internalreferences.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows an exemplifying embodiment of an apparatus for checking thecoverslipping quality of samples onto which a coverslip is applied,

FIG. 2 schematically shows the generation of an image of a coverslippedsample under bright field illumination when an air inclusion is present,

FIG. 3 schematically shows the generation of an image of a coverslippedsample under bright field illumination when a fracture of the coverslipis present, and

FIG. 4 schematically shows the generation of an image with dark fieldillumination.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic general depiction of an exemplifying embodiment ofan apparatus for checking the coverslipping quality of samples 1 ontowhich a coverslip 16 (not depicted in FIG. 1) is applied. The apparatuscomprises a handling apparatus (not depicted in further detail) thatremoves a respective coverslipped sample 1 to be investigated from astacking shelf 2 and places it in a scanning region on a sample stage 3.After each sample 1 has been investigated, the handling apparatus placesthe investigated sample 1 back into stacking shelf 2. These operationsare indicated by the horizontal double arrow.

Stacking shelf 2 can be displaced in a vertical direction, so that afurther sample 1 to be investigated can be brought to the level ofsample stage 3 and then removed. This operation is indicated by thevertical double arrow.

The apparatus for checking coverslipping quality comprises a first lightsource 4 for bright field illumination. First light source 4 emits afirst illumination light bundle 5 that is directed by a beam splitter 6and by a deflection mirror 7 to the coverslipped sample 1 to beinvestigated. Detected light 8 (drawn with dashed lines) reflected fromthe sample travels along the same light path in the opposite direction,i.e. via deflection mirror 7 back to beam splitter 6, passes through thelatter, and lastly arrives at detector 9, which is embodied as a CCDcamera. Detector 9 is located on an electronic circuit board 10 thatcarries an evaluation electronics system (not further depicted).

Also provided are optical components, in particular a telecentric optic,for guiding and shaping the illumination light and detected light, saidcomponents being indicated merely schematically and in exemplifyingfashion as lens 11.

The apparatus furthermore comprises a further light source 12, drawn inmerely schematically, for dark field illumination. Further light source12 can be, in particular, a semi-annular light source.

Provision can be made, for example, that the apparatus for checkingcoverslipping quality outputs an optical or acoustic signal as soon as acoverslipping defect is discovered.

FIG. 2 schematically shows the generation of an image, in particular agrayscale image, under bright field illumination when an air inclusion13 is present under coverslip 14 of a sample 1 located on a specimenslide 15. A light source 4 that emits light toward the coverslippedsample 1 serves for bright field illumination. The light reflected fromthe coverslipped sample 1 is detected with a detector 9 that is embodiedas a camera.

Additional reflections occur in particular at the transition between airinclusion 13 and the material of sample 1 or its coverslipping medium(adhesive), and cause this region to appear particularly bright in thegrayscale image as compared with the background.

FIG. 3 schematically shows the generation of an image, in particular agrayscale image, of a coverslipped sample 1 under bright fieldillumination when a fracture 17, filled with coverslipping medium(adhesive), of coverslip 14 is present. Especially because of theirregular surface structure of fracture 17 and of adhesive 18 that hasemerged in this region, the light emitted from light source 4 isreflected in a different direction from the light that strikes thecoverslipped sample 1 in a region in which a coverslipping defect is notpresent.

The distances, angles, and optical properties are selected in such a waythat none of the light reflected in the region of fracture 17, or only asmall portion of that light, arrives at detector 9. The consequence ofthis is that the region of fractured 17 appears particularly dark in thegrayscale image relative to the background.

Be it noted that in the context of bright field illumination, the angleof incidence of the illumination light does not necessarily need to beequal to 0°. In particular, angles of incidence in the range from 0° to30° relative to the incidence perpendicular, i.e. relative to thevertical in terms of the (unconfirmed) coverslip surface, are also usedin practice in bright field illumination. The position of the detectorin this context should preferably be selected so that no reflectedlight, but instead exclusively refracted and/or scattered light, arrivesat the detector.

FIG. 4 schematically shows the generation of an image, in particular agrayscale image, with dark field illumination. The illumination light oflight source 16 is incident relative to sample 1 at a flat angle, i.e.at a large angle of incidence relative to the surface normal of thecoverslip. Detection occurs with a vertical view onto sample 1.

The image that is generated shows bright, sharply delimited objects withhigh contrast, enabling identification of coverslipping defects, inparticular automatic identification of coverslipping defects. Inparticular, an image of this kind generated under dark fieldillumination makes it possible to check the results of the evaluation ofa previously performed investigation with bright field illumination. Inparticular, it is possible to check whether, for a detected detail ofthe one image, a correspondence is present in the other image.

The invention is not to be limited to the specific embodimentsdisclosed, and modifications and other embodiments are intended to beincluded within the scope of the invention.

PARTS LIST

-   1 Coverslipped sample-   2 Stacking shelf-   3 Sample stage-   4 First light source for bright field illumination-   5 Illumination light bundle-   6 Beam splitter-   7 Deflection mirror-   8 Detected light-   9 Detector-   10 Electronic circuit board-   11 Lens-   12 Further light source-   13 Air inclusion-   14 Coverslip-   15 Specimen slide-   16 Light source for dark field illumination-   17 Fracture of coverslip 14-   18 Emerged adhesive

What is claimed is:
 1. An apparatus, comprising: an optical imagingapparatus configured to automatically check coverslipping quality ofsamples onto which a coverslip is applied, wherein the optical imagingapparatus is configured to automatically check the coverslipping qualityat least partly with dark field illumination; and an automaticevaluation apparatus configured to evaluate at least one image generatedby the imaging apparatus to determine whether one or more of: thecoverslip is damaged after a coverslipping operation; the coverslipexhibits a fracture after a coverslipping operation; air inclusions arepresent in a coverslipping medium; air inclusions are present betweenthe coverslip and the sample; and/or surface irregularities of thecoverslip are present; and wherein the evaluation apparatus is furtherconfigured to automatically check the image generated by the imagingapparatus with regard to a staining quality of a hematoxylin-eosin stainand/or a color intensity.
 2. The apparatus according to claim 1, whereinthe image generated by the imaging apparatus includes a microscopicimage of the coverslip and/or of the coverslipping medium.
 3. Theapparatus according to claim 1, wherein the image generated by theimaging apparatus is a grayscale image.
 4. The apparatus according toclaim 1, further comprising an illumination apparatus configured to: a.illuminate the coverslip and/or the coverslipping medium upon generationof the image and/or b. generate a bright field illumination and/or c.generate a dark field illumination.
 5. The apparatus according to claim1, wherein the imaging apparatus generates both an image with brightfield illumination and an image with dark field illumination, and theevaluation apparatus compares the image with bright field illuminationand the image with dark field illumination.
 6. The apparatus accordingto claim 1, wherein the imaging apparatus generates both an image withbright field illumination and an image with dark field illumination, andthe evaluation apparatus checks as to whether a correspondence ispresent between the image with bright field illumination and the imagewith dark field illumination for a detected detail in one of the imagewith bright field illumination or the image with dark fieldillumination.
 7. The apparatus according to claim 1, wherein the opticalimaging apparatus acquires images at an image acquisition angle and/oran illumination angle, the image acquisition angle and/or theillumination angle being adjustable and/or steplessly adjustable.
 8. Theapparatus according to claim 1, wherein the evaluation apparatus isconfigured to calculate, from a measured average brightness and/orbrightness distribution of a reference image of a coverslipped specimenslide without a sample, an exposure time for generating the image. 9.The apparatus according to claim 1, wherein the evaluation apparatus isconfigured to calculate, from a measured average brightness and/orbrightness distribution of a reference image of a coverslipped specimenslide without a sample, an exposure time for generating the image insuch a way that a predetermined or predeterminable brightness for thebackground is achieved upon generation of the image.
 10. The apparatusaccording to claim 1, wherein the evaluation apparatus carries out, on abasis of a measured brightness and/or brightness distribution of areference image of a coverslipped specimen slide without a sample, ashading correction of the image.
 11. The apparatus according to claim 1,wherein the apparatus is configured to generate an overview image. 12.The apparatus according to claim 1, wherein the apparatus is configuredto read out a barcode attached to a specimen slide or to a coverslip.13. The apparatus according to claim 1, further comprising multipletesting stations, wherein the imaging apparatus is configured to checkthe coverslipping quality in chronologically successive fashion underdifferent conditions and/or at the different testing stations.
 14. Theapparatus according to claim 1, further comprising an automatic handlingapparatus that conveys a coverslipped sample to be investigated into ascanning region of the imaging apparatus.
 15. The apparatus according toclaim 1, further comprising an automatic handling apparatus thatsequentially removes coverslipped samples to be investigated from areceiving apparatus and transfers them into a scanning region of theimaging apparatus.
 16. The apparatus according to claim 1, furthercomprising an automatic handling apparatus that sequentially removescoverslipped samples to be investigated from a receiving apparatus,transfers the coverslipped samples into a scanning region of the imagingapparatus, and deposits each of the coverslipped samples back into thereceiving apparatus after each of the coverslipped samples has beenchecked.
 17. The apparatus according to claim 1, wherein the imagingapparatus is part of a coverslipping machine and/or is integrated into acoverslipping machine.
 18. The apparatus according to claim 1, whereinthe apparatus is automatically configured to receive at least one sampleequipped with a coverslip from a coverslipping machine, or to remove atleast one sample equipped with a coverslip from a coverslipping machine.19. The apparatus according to claim 1, wherein the apparatus is furtherconfigured to, based on results of the evaluation apparatus,re-coverslip a defective coverslipped slide or exclude the defectivecoverslipped slide from at least one microscopic examination and toprovide a non-defective coverslipped slide to a subsequent laboratoryprocess.
 20. A sample processing system, comprising: an apparatus forchecking coverslipping quality comprising an optical imaging apparatusconfigured to automatically check coverslipping quality of a sample ontowhich a coverslip is applied, wherein the optical imaging apparatus isconfigured to automatically check the coverslipping quality at leastpartly with dark field illumination, and wherein the apparatus forchecking coverslipping quality is configured to automatically check animage generated by the optical imaging apparatus with regard to astaining quality of a hematoxylin-eosin stain and/or a color intensity;and a higher-level data processing system: configured to receive dataregarding coverslipping quality, and/or a barcode attached to a specimenslide or to a coverslip, from the apparatus for checking coverslippingquality, and/or; with which the apparatus for checking coverslippingquality exchanges data, and/or; with which the apparatus for checkingcoverslipping quality exchanges data regarding coverslipping quality orwhereabouts of the sample, or regarding patient data to be associatedwith the sample.